NIOSH continues to conduct respirable dust control research for surface mine blasthole drilling operations. Research areas have included testing variables (shroud leakage area, drill deck cross-sectional area, shroud height, collector-to-bailing airflow ratio, etc.) that have the most impact on respirable dust control, development of a dust collector inlet hood, development of a dust collector ...

The hole drilling method is one of the most used semi-destructive techniques for residual stress analysis of mechanical parts. In the presence of non-uniform residual stresses, the stress field can be determined from the measured relaxed strains using several methods, but the most used is the so called integral method. This method is characterized by some simplifications that lead to approximat...

A dual-axis ESPI hole-drilling residual stress measurement method is described. It has the advantage of evaluating all the in-plane normal stress components with similar response to measurement errors, significantly lower than with single-axis measurements. Experimental tests were done on a stressed specimen, and the results supported theoretical expectations.

We describe several scenarios of basic femtosecond machining and materials processing that should lead to practical applications. Included are results on high through-put deep hole drilling in polymers and glasses in ambient air, and precision high speed micron-scale surface modification of materials.

in manufacturing industry, it has been acknowledged that tool wear prediction has an important role in higher quality of products and acceptable efficiency. being an emerging area of research in recent years, drilling tool wear is an important factor which directly affects quality parameters of machined hole such as hole centring, roundness, burr formation and finished surface. in this paper, t...

abstract: the equal channel angular rolling (ecar) is one of the severe plastic deformation processes, which can develop a shear deformation into a sheet metal. in this process, internal stresses are created due to the different strain levels experienced in different locations at the same time. the incremental hole drilling method is an effective technique for the evaluation of the through-thic...

Laser micromachining has the capability to fabricate very small and basic 2.5 D geometric features on a range of materials in the form of laser ablation or irradiation. Short pulsed lasers that can achieve wide range of wavelengths in the form of harmonics of infrared laser beam at 1064 nm wavelength have been a very effective micro-machining tool used for hole drilling, cutting, scribing, trim...

The interaction between friction and vibration is a widely recognised source of inefciency in all mechanical systems. The nature of this interaction is very dependent on the dynamic environment and its control requires a detailed understanding of the mathematical structure governing the stability of this environment. Although the fundamental causes of friction-induced intermittent motion have b...

Research on the use of high pressure water jet systems to date has mainly concentrated on laboratory simulation tests and field trials on the surface. The effects of field stress have only been simulated, therefore, by sample confinement in triaxial chambers. This paper contrasts such results with data obtained from a test site located 1000 ft below the surface in a stressed barrier pillar. Dat...

Steel plates with open holes are commonly used in structural assemblies. The fatigue properties of such details are influenced by bolted clamp-up and hole fabrication methods. The fracture surface, stiffness degradation and fatigue life of test specimens are investigated in detail and compared with the contemporary test data. The analysis results show that the presence of draglines greatly infl...